Pontoon boats are a popular watercraft with many people as they can be used for many different activities such as fishing, trolling, tubing, skiing, cruising and mooring. The decks for pontoon boats most often provided with an enclosure that extends about 2–3 feet above the deck to offer protection against stepping into the water or being ejected into the water during movement of the boat in a body of water. The enclosure has at least one and more often two gates to allow a person to directly walk from a pier onto the deck with gate matching the enclosure such that a uniform appearance is provided from the front to the rear of the boat. A popular activity for the use of a pontoon boat is to moor in a body of water and allow the deck to be used as a platform for swimmers. A ladder may be provided for a swimmer to move from the water onto the deck. It is common for such a ladder to be stored in seat furniture located on the deck and when needed the ladder is attached to catches mounted in a gateway of the enclosure. When the ladder is located in the gateway, the gate can not be closed and it is possible that ladder may be dislodged from the deck by a wave created by another boat passing the moored watercraft and as a result a ladder often sinks to the bottom the body of water. Unfortunately, a ladder stored inside a seat is often not accessible from the water and nor convenient for speedy installation in the gateway. U.S. Pat. No. 4,846,303 and U.S. patent application Ser. No. 10/772,125 disclose ladder structure that is attached to the exterior surface of the deck and moved in a track between an up position adjacent the gate and a down position inline with the gate. While this type structure functions in an adequate manner, a track may be damaged if the watercraft should engage the dock at a high speed. In addition, since the ladder and track is located on the exterior of the deck some boat owners have a concern that it detracts from the overall sleek appearance of the watercraft.